Homopolymers of 4-methyl-1-pentene have some properties which are particularly desirable such as transparency. It has been discovered by those skilled in the art, however, that certain properties of such polymers can be improved by incorporating comonomers. Some examples of processes for preparing copolymers of 4-methyl-1-pentene are disclosed in U.S. Pat. Nos. 3,489,735 and 4,146,591, the disclosures of which are incorporated herein by reference.
The homopolymerization and copolymerization of 4-methyl-1-pentene is generally carried out in a batch polymerization process. The term "batch polymerization" is used to refer to a polymerization in which a quantity of the monomers are polymerized in a reaction vessel and then the resulting polymer is recovered from that reaction vessel upon the desired level of polymerization of the monomers. It is also known in the art that it is desirable to carry out such polymerizations under conditions which result in a slurry of particles of the desired polymer or copolymer in the polymerization diluent rather than a solution of the polymer or copolymer. The formation of such a slurry aids in the separation and purification of the resulting polymer.
The present applicants have conducted a large number of batch copolymerizations of 4-methyl-1-pentene copolymers using techniques such as those taught in the art. One of the facts that the applicants have noted in using such prior art disclosed processes is that polymeric materials are formed which dissolve in the polymerization diluent. The presence of the soluble polymeric materials has been noted to often coat the interior of the reaction vessel. If such polymeric materials are allowed to accumulate over successive batches of polymers, the soluble polymer can result in significant reductions in the efficiency of heat transfer in the reactor. Accordingly, in using polymerization processes of the type taught in the prior art, it has been necessary to thoroughly wash the reaction vessel periodically to assure that soluble polymeric material is removed from the reaction vessel before additional batch polymerizations of 4-methyl-1-pentene are conducted.
In addition, the applicants have noted that it becomes increasingly difficult to keep the copolymer in the undissolved particle form as the level of comonomer is increased and as the temperature of polymerization is increased. This phenomena is particularly noticeable when the comonomer is a linear olefin containing 11 carbons or more. Since catalyst activity and thus productivity is directly related to the polymerization temperature it is desirable to carry out such polymerizations at temperatures of at least about 50.degree. C.
Obviously, it would be advantageous to have a process for producing such copolymers of 4MP1 which would minimize the formation of such soluble polymeric material.
An object of the present invention is to provide processes which reduce the amount of soluble polymeric material produced in a batch slurry copolymerization of 4-methyl-1-pentene. Other aspects, objects, and advantages of the present invention will be apparent to those skilled in the art having the benefit of the following disclosure.